Rough Layer for Better Anti-Stiction Deposition

ABSTRACT

A microelectromechanical systems (MEMS) package with roughness for high quality anti-stiction is provided. A device substrate is arranged over a support device. The device substrate comprises a movable element with a lower surface that is rough and that is arranged within a cavity. A dielectric layer is arranged between the support device and the device substrate. The dielectric layer laterally encloses the cavity. An anti-stiction layer lines the lower surface of the movable element. A method for manufacturing the MEMS package is also provided.

BACKGROUND

Microelectromechanical systems (MEMS) devices, such as accelerometers,pressure sensors, and gyroscopes, have found widespread use in manymodern day electronic devices. For example, MEMS accelerometers arecommonly found in automobiles (e.g., in airbag deployment systems),tablet computers, or in smart phones. For many applications, MEMSdevices are electrically connected to application-specific integratedcircuits (ASICs) to form complete MEMS systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A illustrates a cross-sectional view of some embodiments of amicroelectromechanical systems (MEMS) package with roughness for highquality anti-stiction.

FIG. 1B illustrates an enlarged cross-sectional view of some embodimentsof a movable element in the MEMS package of FIG. 1A.

FIG. 2A illustrates a cross-sectional view of some more detailedembodiments of the MEMS package of FIG. 1A.

FIG. 2B illustrates a cross-sectional view of other more detailedembodiments of the MEMS package of FIG. 1A.

FIGS. 3-10 illustrate a series of cross-sectional views of someembodiments of a method for manufacturing a MEMS package with roughnessfor high quality anti-stiction.

FIG. 11 illustrates a flowchart of some embodiments of a method formanufacturing a MEMS package with roughness for high qualityanti-stiction.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Some microelectromechanical systems (MEMS) devices, such asaccelerometers, gyroscopes, and pressure sensors, comprise a movableelement and neighboring sensing electrodes arranged within a cavity. Themovable element is configured to move in proportion to external stimuli,such as acceleration, pressure, or gravity. The sensing electrodes areconfigured to sense the extent of the movement using capacitive couplingwith the movable element.

A challenge with the MEMS devices is stiction. When the movable elementmoves to such an extreme that it interfaces with surfaces of the cavity,the movable element may stick to the surfaces of the cavity. Suchstiction reduces the sensitivity of the MEMS devices and reduces thelifetimes of the MEMS devices. A solution to stiction is to coatsurfaces of the cavity and/or surfaces of the movable element with ananti-stiction layer. The anti-stiction layer may be formed by a reactionbetween perfluorodecyltrichlorosilane (FDTS) and hydroxide on thesurfaces. However, the reaction is often performed without heat andwithout plasma, such that the quality of the reaction is dependent uponcollisions of the FDTS with the surfaces. Given that the surfaces of thecavity and/or the movable element are often flat and arranged at 90degree angles relative to one another, the surface area with which theFDTS may contact the hydroxide may be minimal and the quality of thereaction may be poor. Poor reaction quality leads to an anti-stictionlayer with poor thickness uniformity and/or poor coverage.

The present application is directed to a MEMS package with roughness forhigh quality anti-stiction. In some embodiments, a device substrate isarranged over a support device and covered by a capping device. Thedevice substrate comprises a movable element arranged within a cavitybetween the support and capping devices, and the movable elementcomprises a rough surface. An anti-stiction layer lines the roughsurface and other surfaces of the device substrate and the cappingdevice within in the cavity.

Advantageously, the likelihood of stiction between surfaces of thecavity and the rough surface of the movable element is low due to theroughness of the rough surface. The roughness (by way of peaks andvalleys) minimizes the surface area of the rough surface that mayinterface with the surfaces of the cavity. Further, where theanti-stiction layer is formed by FDTS, the roughness increases thesurface area to which FDTS may contact hydroxide on the movable element,thereby increasing the quality of the anti-stiction layer. Even more,the MEMS package can be formed without additional masks (which addcost), and without affecting bond interfaces between the devicesubstrate and the capping and support devices.

With reference to FIG. 1A, a cross-sectional view 100A of someembodiments of a MEMS package with roughness for high qualityanti-stiction is provided. As illustrated, a MEMS device substrate 102is arranged over a support device 104 and covered by a capping device106. The MEMS device substrate 102 is bonded to the support and cappingdevices 104, 106, and spaced from the support device 104 by aninter-substrate dielectric (ISD) layer 108. In some embodiments, theMEMS device substrate 102 is fusion bonded to the capping device 106and/or eutectically bonded to the support device 104 through respectivebond rings 110, 112 of the MEMS device substrate 102 and the supportdevice 104. Further, in some embodiments, the support and/or the cappingdevices 104, 106 are integrated circuits (ICs).

A movable element 114 (e.g., a proof mass) of the MEMS device substrate102 is suspended within a cavity 116 defined between the support andcapping devices 104, 106, and is configured to move within the cavity116 in proportion to external stimuli, such as acceleration. A lowersurface 118 of the MEMS device substrate 102, including a lower surface120 of the movable element 114, is rough within the cavity 116. Forexample, the lower surface 118 of the MEMS device substrate 102 may havea saw tooth profile and/or peaks and valleys of varying size within thecavity 116. As such, the MEMS device substrate 102 may, for example,also be referred to as a rough layer. An anti-stiction layer 122 isarranged in the cavity 116, and lines surfaces of the capping device 106and the MEMS device substrate 102 within the cavity 116, including themovable element lower surface 120.

Roughness on the movable element lower surface 120 advantageouslyreduces the likelihood of stiction between the movable element 114 andan upper surface 124 of the support device 104. The roughness reducesthe amount of surface area on the movable element lower surface 120 thatcan come into contact with the support device upper surface 124. Forexample, if the movable element 114 moves towards the support deviceupper surface 124, the largest protrusion of the movable element lowersurface 120 is going to interface with the support device upper surface124 first and prevent other regions on the movable element lower surface120 from interfacing with and sticking to the support device uppersurface 124. Further, where the anti-stiction layer 122 is formed usinga reaction between FDTS and hydroxide, roughness on the movable elementlower surface 120 advantageously increases the surface area for thereaction and hence the quality of the anti-stiction layer 122 on themovable element lower surface 120. As such, a thickness of theanti-stiction layer 122 is more uniform on the movable element lowersurface 120 than it is on other flat surfaces.

With reference to FIG. 1B, an enlarged cross-sectional view 100B of someembodiments of the movable element lower surface 120 is provided. Asillustrated, a surface area of the movable element lower surface 120 isgreater than an upper surface 126 of the movable element 114, eventhough the movable element upper surface 126 and the movable elementlower surface 120 share a common footprint. This is because the movableelement lower surface 120 is rough and spans three-dimensions, whereasthe movable element upper surface 126 is substantially planar andrestricted to two dimensions. Where the anti-stiction layer 122 isformed by FDTS, the increased surface area of the movable element lowersurface 120 increases the quality of a region 128 of the anti-stictionlayer 122 on the movable element lower surface 120 relative to otherregions of the anti-stiction layer 122. For example, a thickness T₁ ofthe anti-stiction layer 122 on the movable element lower surface 120 maybe substantially uniform, whereas a thickness T₂ of the anti-stictionlayer 122 on the movable element upper surface 126 may be substantiallynon-uniform.

While the movable element 114 is illustrated and described as beingsuspended within the cavity 116 between the support and capping devices104, 106, the capping device 106 may be omitted and the movable element114 may be a flexible membrane covering the cavity 116 in otherembodiments. In such embodiments, the movable element 114 defines anupper surface of the cavity 116 and configured to deflect in proportionto external stimuli, such as pressure. Such a configuration may, forexample, be used for sensing a pressure difference between the cavity116 and an external environment of the MEMS package.

With reference to FIG. 2A, a cross-sectional view 200A of some moredetailed embodiments of the MEMS package of FIG. 1A is provided. Asillustrated, a support device 104 comprises a device region 202 arrangedon an upper surface of a support substrate 204, and an interconnectstructure 206 covering the device region 202 and the support substrate204. The device region 202 comprises electronic devices 208, 210, 212,such as transistors, photodiodes, memory cells, etc. The supportsubstrate 204 may be, for example, a bulk semiconductor substrate, suchas a bulk silicon substrate, or a silicon-on-insulator (SOI) substrate.

The interconnect structure 206 interconnects the electronic devices 208,210, 212 in the device region 202. A stack of conductive layers 214, 216(only two of which are labeled) are arranged within a dielectric region218 comprising multiple inter-layer dielectric (ILD) layers and apassivation layer. The conductive layers 214, 216 comprise individualfeatures 220, 222 (only some of which are labeled), such as lines andpads, and a topmost conductive layer 216 comprises a support bond ring112 and a fixed sensing electrode 224. The support bond ring 112 extendslaterally to enclose a cavity 116 overlying the support device 104, andthe fixed sensing electrode 224 is arranged under the cavity 116. Vias226, 228 (only some of which are labeled) are arranged in the dielectricregion 218, between the conductive layers 214, 216, to interconnect theconductive layers 214, 216. Similarly, contacts 230 (only one of whichis labeled) are arranged in the dielectric region 218, between abottommost conductive layer (not labeled) and the device region 202, toconnect the device region 202 to the bottommost conductive layer. Theconductive layers 214, 216, the vias 226, 228, and the contacts 230 maybe, for example, a metal, such as copper, aluminum copper, or tungsten,or some other conductive material. The dielectric region 218 may be orotherwise include, for example, an oxide, a low κ dielectric (i.e., adielectric with a dielectric constant less than about 3.9), or someother dielectric material.

An ISD layer 108 and a device bond ring 110 are stacked over the supportdevice 104, between the support device 104 and a MEMS device substrate102. The ISD layer 108 and the device bond ring 110 laterally enclosethe cavity 116 and bond the MEMS device substrate 102 to the supportdevice 104 at an interface between the support bond ring 112 and thedevice bond ring 110. The ISD layer 108 is arranged over the device bondring 110, between the device bond ring 110 and the MEMS device substrate102. The ISD layer 108 may be, for example, a thermal oxide or someother dielectric material. The device bond ring 110 underlies the ISDlayer 108 and interfaces with the support bond ring 112. In someembodiments, the device bond ring 110 interfaces with the support bondring 112 at a eutectic bond. Further, the device bond ring 110 overlapswith the support bond ring 112 and has a ring-shaped footprint ofsimilar or equal size (e.g., in terms of area) as that of the supportbond ring 112. The device bond ring 110 may be, for example, germaniumor some other conductive material.

The MEMS device substrate 102 is arranged over and bonded to the supportdevice 104 through the ISD layer 108 and the device bond ring 110. TheMEMS device substrate 102 comprises a fixed region 232 and a movableelement 114 (i.e., a movable region), and may be, for example, a bulksemiconductor substrate, such as a monocrystalline silicon substrate.The fixed region 232 corresponds to regions of the MEMS device substrate102 that are fixed relative to the movable element 114. The movableelement 114 corresponds to a region of the MEMS device substrate 102that is suspended within the cavity 116, over the fixed sensingelectrode 224, and is configured to move within the cavity 116 inproportion to external stimuli, such as acceleration. The movableelement 114 is suspended by one or more cantilever beams or springs (notshown) that connect the movable element 114 to the fixed region 232.Further, the movable element 114 comprises a movable sensing electrode(not shown) that is electrically coupled to the support device 104 bythrough substrate vias (TSVs) 234, 236 extending through the MEMS devicesubstrate 102 and the ISD dielectric layer 108 to, for example, thedevice bond ring 110. The TSVs 234, 236 may, for example, comprise ametal or some other conductive material.

A capping device 106 is arranged over and bonded to the MEMS devicesubstrate 102. In some embodiments, the capping device 106 is bonded tothe MEMS device substrate 102 by a fusion bond or hybrid bond at aninterface between the capping device 106 and the MEMS device substrate102. The hybrid bond may, for example, comprise a bond interface betweendielectric materials and a bond interface between some other materials,such as metals. The capping device 106 defines an upper surface of thecavity 116 and, in some embodiments, comprises a lower recess 238defining an upper region of the cavity 116. The capping device 106 maybe, for example, IC or a bulk semiconductor substrate, such as a bulksilicon substrate.

An anti-stiction layer 122 lines a lower surface 118 of the MEMS devicesubstrate 102, including a lower surface 120 of the movable element 114.The MEMS device lower surface 118 and the movable element lower surface120 are rough and may have, for example, a saw tooth profile with teethof varying size. Further, the anti-stiction layer 122 lines othersurfaces of the MEMS device substrate 102 and the capping device 106within the cavity 116, such as, for example, the lower recess 238 of thecapping device 106. The anti-stiction layer 122 is a material configuredto reduce stiction between the movable element 114 and surface of thecavity 116. The anti-stiction layer 122 may be, for example, a FDTSmonolayer or some other self-assembled monolayer (SAM). The FDTSmonolayer results from a reaction between FDTS and hydroxide on surfacesof the MEMS device substrate 102 and the capping device 106.

In operation, the movable element 114 moves within the cavity 116 inproportion to external stimuli, such as acceleration. For example, asthe MEMS package is accelerated, the movable element 114 moves withinthe cavity 116 in proportion to the acceleration. Capacitive couplingbetween the fixed sensing electrode 224 and the movable sensingelectrode (not shown) is then used to measure the movement of themovable element 114 and to indirectly measure the external stimuli.

In some instances, the movable element 114 may move beyond limits andinterface with surfaces of the cavity 116, thereby opening up thepossibility of stiction between the movable element 114 and thesurfaces. However, due to the anti-stiction layer 122 and the roughnesson the MEMS device lower surface 118, there is advantageously a lowlikelihood of stiction. The roughness minimizes the amount of surfacearea on the movable element lower surface 120 that can come into contactwith an upper surface 124 of the support device 104. Further, where theanti-stiction layer 122 is the FDTS monolayer, the roughness on themovable element lower surface 120 increases the quality of theanti-stiction layer 122 on the movable element lower surface 120 sincethe quality is dependent upon the amount of surface area on the movableelement lower surface 120 and the roughness increases surface area.

With reference to FIG. 2B, a cross-sectional view 200B of other moredetailed embodiments of the MEMS package of FIG. 1A. As illustrated, thecapping device 106 (see FIG. 2A) is omitted. Further, the movableelement 114 is a flexible membrane defining an upper surface of thecavity 116 and is configured to deflect in proportion to externalstimuli, such as pressure. Even more, in some embodiments, the supportdevice 104 is bonded to the MEMS device substrate 102 by fusion bondingand/or electrically coupled to the MEMS device substrate 102 by bondpads 240, 242 of the support device 104.

While the position of the movable element 114 is illustrated anddescribed as being determined by capacitive coupling between sensingelectrodes in FIGS. 2A and 2B, other approaches may be employed to sensethe position of the movable element 114 within the cavity 116. Forexample, optical approaches may be employed to sense the position of themovable element 114 with the cavity 116.

With reference to FIGS. 3-10, a series of cross-sectional views of someembodiments of a method for manufacturing a MEMS package with roughnessfor high quality anti-stiction is provided. The cross-sectional viewsmay, for example, correspond to the MEMS package of FIG. 1A at variousstages of manufacture.

As illustrated by the cross-sectional view 300 of FIG. 3, a MEMS devicesubstrate 102 is arranged over and bonded to a capping device 106. Insome embodiments, the MEMS device substrate 102 and the capping device106 are bonded by a fusion bond at an interface 302 between the MEMSdevice substrate 102 and the capping device 106. The MEMS devicesubstrate 102 and the capping device 106 may be, for example, a bulksemiconductor substrate, such as a bulk monocrystalline siliconsubstrate. The capping device 106 comprises a recess 238 arranged on anupper side of the capping device 106, between the capping device 106 andthe MEMS device substrate 102. In some embodiments, the recess 238 isformed by photolithography (not shown) before bonding the capping device106 and the MEMS device substrate 102 together. For example, aphotoresist layer may be formed and patterned on the capping device 106.An etchant may then be applied to the capping device 106 while thephotoresist layer selectively masks the capping device.

Also illustrated by the cross-sectional view 300 of FIG. 3, the MEMSdevice substrate 102 is thinned to a desired thickness T. In someembodiments, the MEMS device substrate 102 is thinned by a chemicalmechanical polish (CMP) and/or an etch back.

As illustrated by the cross-sectional view 400 of FIG. 4, an ISD layer108 is formed over the MEMS device substrate 102. The ISD layer 108 isan oxide, such as silicon dioxide, and is formed by thermal oxidation.In performing the thermal oxidation, regions of the MEMS devicesubstrate 102 neighboring the ISD layer 108 are consumed and convertedto the ISD layer 108 by a reaction between an oxidizing agent and theMEMS device substrate 102. The oxidizing agent is introduced into anenvironment of the MEMS device substrate 102 and diffuses into the MEMSdevice substrate 102 to react with the MEMS device substrate 102. Theoxidizing agent may be, for example, water vapor or molecular oxygen,and is introduced at high temperature (e.g., between about 800-1200degrees Celsius). The reaction results in a surface 118 of the MEMSdevice substrate 102 that is rough. For example, the surface 118 of theMEMS device substrate 102 may have a saw tooth profile with teeth ofvarying size. As such, the MEMS device substrate 102 may, for example,also be referred to as a rough layer.

As illustrated by the cross-sectional view 500 of FIG. 5, a first etchis performed into the ISD layer 108 to remove a region of the ISD layer108 that overlies the recess 238 of the capping device 106 (i.e., toform an opening). In some embodiments, the region is restricted todirectly over the recess 238. By removing the region of the ISD layer108 overlying the recess 238, the rough surface 118 of the MEMS devicesubstrate 102 is partially exposed.

In some embodiments, the process for performing the first etch comprisesdepositing and patterning a first photoresist layer over the ISD layer108. For example, the first photoresist layer may be patterned to maskregions of the ISD layer 108 that laterally surround the recess 238. Thepatterning may advantageously be performed with a same photolithographicmask used to form the recess 238, such that no additional masks may beneeded to pattern the photoresist layer. Thereafter, one or moreetchants 502, such as wet or dry etchants, are applied to the ISD layer108 while using the first patterned photoresist layer 504 as a mask.After performing the first etch, the first patterned photoresist layer504 is removed or otherwise stripped.

As illustrated by the cross-sectional view 600 of FIG. 6, a bond ringlayer 602 is formed over the ISD layer 108 and the MEMS device substrate102. The bond ring layer 602 may be formed of, for example, germanium orsome other material capable of eutectic bonding. In some embodiments,the bond ring layer 602 is formed using a vapor deposition technique,such as chemical vapor or physical vapor deposition, or atomic layerdeposition.

As illustrated by the cross-sectional view 700 of FIG. 7, a second etchis performed into the bond ring layer 602 (see FIG. 6) to form a devicebond ring 110 laterally enclosing the recess 238. In some embodiments,the process for performing the second etch comprises depositing andpatterning a second photoresist layer over the bond ring layer 602. Forexample, the second photoresist layer may be patterned to mask regionsof the bond ring layer 602 that correspond to the device bond ring 110.Thereafter, one or more etchants 702, such as wet or dry etchants, areapplied to the bond ring layer 602 while using the second patternedphotoresist layer 704 as a mask. After performing the second etch, thepatterned photoresist layer 704 is removed or otherwise stripped.

As illustrated by the cross-sectional view 800 of FIG. 8, a third etchis performed into the MEMS device substrate 102 to form a movableelement 114 over the recess 238. In some embodiments, the process forperforming the third etch comprises depositing and patterning a thirdphotoresist layer over ISD layer 108 and the MEMS device substrate 102.For example, the third photoresist layer may be patterned to maskregions of the MEMS device substrate 102 that correspond to the movableelement 114 and regions of the MEMS device substrate 102 and the ISDlayer 108 laterally surrounding the recess 238. Thereafter, one or moreetchants 802, such as wet or dry etchants, are applied to the MEMSdevice substrate 102 while using the third patterned photoresist layer804 as a mask. After performing the third etch, the third patternedphotoresist layer 804 is removed or otherwise stripped.

As illustrated by the cross-sectional view 900 of FIG. 9, ananti-stiction layer 122 is formed lining surfaces 902 (only one of whichis labeled) of the recess 238 and surfaces of the MEMS device substrate102 overlying the recess 238, such as portions of the rough surface 118overlying the recess 238. In some embodiments, the anti-stiction layer122 is formed by exposing the surfaces to FDTS. The FDTS may, forexample, be exposed to the surfaces in the absence of heat and withoutplasma. The FDTS reacts with hydroxyl (—OH) groups on the surfaces toterminate dangling bonds of the surfaces and to covalently bond to thesurfaces. The FDTS reacts and covalently bonds to form the anti-stictionlayer 122 as a FDTS monolayer that is self-aligned due to van der Waalsintermolecular forces. Advantageously, because the surface area of therough surface 118 is greater than flat surfaces, the quality of theanti-stiction layer 122 is greater (e.g., more uniform) on the roughsurface 118 than on other surfaces.

The FDTS reaction is dependent upon hydroxyl (—OH) groups on thesurfaces.

Therefore, in some embodiments, the surfaces are hydrolyzed prior toforming the anti-stiction layer 122. Hydrolysis may include theapplication of purified water, such as deionized or distilled water, tothe surfaces. Further, hydrolysis may be enhanced by an acid or a base.In some embodiments, hydrolysis comprises treating the surfaces with anacidic solution. For example, the surfaces may be treated with asolution comprising hydrofluoric acid, such as dilute hydrofluoric acid(DHA) or buffer oxide etch (BOE).

As illustrated by the cross-sectional view 1000 of FIG. 10, MEMS devicesubstrate 102 and the capping device 106 are rotated 180 degrees andbonded to a support device 104. The support device 104 may be, forexample, an IC or a bulk semiconductor substrate. In some embodiments,the MEMS device substrate 102 is eutectically bonded to the supportdevice 104 through a support bond ring 112 of the support device 104.The support bond ring 112 has the same or a similar footprint as thedevice bond ring 110, and may be, for example, aluminum copper or someother material capable of eutectic bonding.

With reference to FIG. 11, a flowchart 1100 of some embodiments of amethod for manufacturing a MEMS package with roughness for a highquality anti-stiction layer is provided.

At 1102, MEMS device substrate is bonded to a capping device. Thecapping device comprises a recess between the capping device and theMEMS device substrate. See, for example, FIG. 3.

At 1104, a thermal oxide layer is formed on the MEMS device substrate,opposite the capping device. Forming the thermal oxide layer roughensthe MEMS device substrate at an interface with the thermal oxide layer.See, for example, FIG. 4.

At 1106, a first etch is performed into the thermal oxide layer toremove a region of the thermal oxide layer overlying the recess in thecapping device. The first etch exposes a rough surface of the MEMSdevice substrate. See, for example, FIG. 5.

At 1108, a device bond ring is formed on the thermal oxide layer. See,for example, FIGS. 6 and 7.

At 1110, a second etch is performed into the MEMS device substrate toform a movable element over the recess. See, for example, FIG. 8.

At 1112, an FDTS monolayer is formed lining the rough surface andsurfaces of the recess. See, for example, FIG. 9.

At 1114, the capping device and the MEMS device substrate are bonded toa support device through the thermal oxide layer. See, for example, FIG.10.

Advantageously, the method may be performed without affecting the bondquality between the MEMS device substrate and the capping device.Further, the method adds no additional masks, which advantageously keepscosts low. Even more, the method advantageously achieves low stictionbetween the movable element and the support device.

While the flowchart 1100 is directed to the MEMS package of FIG. 1A andFIG. 2A, Acts 1102, 1108, and 1110 may be omitted in other embodimentsto form a MEMS package according to the embodiments of FIG. 2B. Further,while the method described by the flowchart 1100 is illustrated anddescribed herein as a series of acts or events, it will be appreciatedthat the illustrated ordering of such acts or events are not to beinterpreted in a limiting sense. For example, some acts may occur indifferent orders and/or concurrently with other acts or events apartfrom those illustrated and/or described herein. Further, not allillustrated acts may be required to implement one or more aspects orembodiments of the description herein, and one or more of the actsdepicted herein may be carried out in one or more separate acts and/orphases.

Thus, as can be appreciated from above, the present disclosure providesa MEMS package. A device substrate is arranged over a support device.The device substrate comprises a movable element with a lower surfacethat is rough and that is arranged within a cavity. A dielectric layeris arranged between the support device and the device substrate. Thedielectric layer laterally encloses the cavity. An anti-stiction layerlines the lower surface of the movable element.

In other embodiments, the present disclosure provides a method formanufacturing a MEMS package. A thermal oxide layer is formed on asurface of a device substrate. Forming the thermal oxide layer roughensthe surface of the device substrate. An etch is performed into thethermal oxide layer to form an opening partially exposing the surface ofthe device substrate. An anti-stiction layer is formed lining thepartially-exposed surface of the device substrate. The device substrateis bonded to a support device through the thermal oxide layer to seal acavity overlying the support device.

In yet other embodiments, the present disclosure provides a MEMSpackage. A capping device is arranged over a support device. A devicesubstrate is arranged between the support and capping devices. Thedevice substrate comprises a movable element arranged within a cavitybetween the support and capping devices. A lower surface of the movableelement is rough. A dielectric layer is arranged between the supportdevice and the device substrate. The dielectric layer laterally enclosesthe cavity. An anti-stiction layer lines the lower surface of themovable element.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A microelectromechanical systems (MEMS) package comprising: a devicesubstrate arranged over a support device, wherein the device substratecomprises a movable element with a lower surface that is rough and thatis arranged within a cavity; a dielectric layer arranged between thesupport device and the device substrate, wherein the dielectric layerlaterally encloses the cavity; and an anti-stiction layer lining thelower surface of the movable element.
 2. The MEMS package according toclaim 1, further comprising: a capping device arranged over the devicesubstrate and defining an upper surface of the cavity, wherein themovable element is suspended with the cavity.
 3. The MEMS packageaccording to claim 2, wherein the cavity comprises a recess on a lowerside of the capping device, and wherein the anti-stiction layer linesthe recess on the lower side of the capping device.
 4. The MEMS packageaccording to claim 1, wherein the dielectric layer is a thermal oxidelayer, and wherein the device substrate is monocrystalline silicon. 5.The MEMS package according to claim 1, wherein the dielectric layerdirectly abuts the device substrate.
 6. The MEMS package according toclaim 1, wherein a lower surface of the device substrate is rough andincludes the lower surface of the movable element.
 7. The MEMS packageaccording to claim 1, wherein the lower surface of the movable elementcomprises a sawtooth profile.
 8. The MEMS package according to claim 1,wherein the movable element is configured to move within the cavity inproportion to external stimuli.
 9. The MEMS package according to claim1, wherein the anti-stiction layer is a perfluorodecyltrichlorosilane(FDTS) monolayer.
 10. The MEMS package according to claim 1, wherein aregion of the anti-stiction layer lining the lower surface of themovable element has a substantially uniform thickness, whereas anotherregion of the anti-stiction layer overlying the region has asubstantially non-uniform thickness. 11-19. (canceled)
 20. Amicroelectromechanical systems (MEMS) package comprising: a cappingdevice arranged over a support device; a device substrate arrangedbetween the support and capping devices, wherein the device substratecomprises a movable element arranged within a cavity between the supportand capping devices, and wherein a lower surface of the movable elementis rough; a dielectric layer arranged between the support device and thedevice substrate, wherein the dielectric layer laterally encloses thecavity; and an anti-stiction layer lining the lower surface of themovable element.
 21. The MEMS package according to claim 20, wherein atop of the dielectric layer is rough, and wherein a bottom of the devicesubstrate is rough and complements the top of the dielectric layer. 22.The MEMS package according to claim 21, wherein the dielectric layer hasa pair of inner opposite sidewalls in the cavity, wherein the dielectriclayer has a pair of outer opposite sidewalls outside of the cavity,wherein the inner opposite sidewalls are spaced between the outeropposite sidewalls, and wherein the top of the dielectric layer is roughcontinuously from the outer opposite sidewalls respectively to the inneropposite sidewalls.
 23. The MEMS package according to claim 20, whereinthe dielectric layer underlies and contacts the device substrate,wherein the dielectric layer is silicon dioxide, and wherein the devicesubstrate is a bulk monocrystalline silicon substrate.
 24. The MEMSpackage according to claim 20, wherein the capping device comprises abottom recess that partially defines the cavity and that is directlyover the movable element.
 25. The MEMS package according to claim 20,wherein the anti-stiction layer extends continuously from a firstsidewall of the anti-stiction layer to a second sidewall of theanti-stiction layer, wherein the first and second sidewalls of theanti-stiction layer respectively contact opposite sidewalls of thecavity, wherein the anti-stiction layer contacts top and bottom surfacesof the device substrate, a sidewall of the device substrate, and thecapping device while extending continuously from the first sidewall ofthe anti-stiction layer to the second sidewall of the anti-stictionlayer.
 26. The MEMS package according to claim 20, wherein theanti-stiction layer has a ring-shaped profile encircling and contactingthe movable element, and wherein a bottom surface of the anti-stictionlayer is rough.
 27. A microelectromechanical systems (MEMS) packagecomprising: a first semiconductor substrate; an interconnect structureon the first semiconductor substrate, wherein the interconnect structurecomprises an interlayer dielectric (ILD) layer and a stack of conductivefeatures within the dielectric layer; a device layer in the firstsemiconductor substrate, between the first semiconductor substrate andthe interconnect structure; an inter-substrate dielectric (ISD) layerover and bonded to interconnect structure, wherein the ISD layercomprises a cavity and is silicon dioxide; a second semiconductorsubstrate covering and contacting the ISD layer, wherein the secondsemiconductor substrate comprises a movable element within the cavity,wherein a lower surface of the movable element is rough, and wherein thesecond semiconductor substrate is a bulk substrate of monocrystallinesilicon; a through substrate via (TSV) extending through the secondsemiconductor substrate and the ISD layer to electrically couple withthe interconnect structure; and an anti-stiction layer lining andcontacting the movable element.
 28. The MEMS package according to claim27, further comprising: a capping device covering and bonded to thesecond semiconductor substrate, wherein the capping device comprises abottom recess partially defining the cavity and lined by theanti-stiction layer.
 29. The MEMS package according to claim 27, whereinthe ISD layer has a pair of inner opposite sidewalls in the cavity,wherein the ISD layer has a pair of outer opposite sidewalls outside ofthe cavity, wherein the inner opposite sidewalls are spaced between theouter opposite sidewalls, and wherein a bottom of the secondsemiconductor substrate is rough continuously from one of the outeropposite sidewalls to another one of the outer opposite sidewalls.